1. Field of the Invention
This invention relates to permanent building blocks having voids which may be used to form a reinforced concrete framework extending through a plurality of the stacked blocks, and to a reinforced concrete structure employing such blocks.
So called "reinforced concrete buildings" typically employ a reinforced concrete framework including vertical columns and horizontal tying elements which cooperate to form a grid, and a superstructure providing inner and outer wall surfaces, insulation, vapor barrier and the like, supported on the framework. These structures have traditionally been formed by first erecting the reinforced framework using specially erected forms which often include reusable modules. After a section of the concrete framework had cured the forms were removed and the separate elements of the superstructure were successively joined to the framework. This method of construction involves a great deal of manual labor in erecting and dismantling the forms and mounting the separate superstructure components such as inner and outer wall surfaces, insulation, vapor barrier material and the like, on the reinforced concrete framework.
In recent years, a variety of building blocks have been proposed which are designed to provide the elements of a superstructure for a reinforced concrete building and also contain voids which act as forms for the erection of the concrete framework. These blocks may be stacked so that the voids in adjacent blocks are aligned. Reinforcing rods are inserted in the voids and then the concrete is poured. When the concrete cures, the wall structure is complete with the block material providing the inner and outer wall surfaces, the insulation, vapor barrier and the like. These blocks have the potential of providing an important saving in time and labor in the on-site construction of reinforced concrete buildings. U.S. Pat. No. 3,782,049 issued to one of the co-inventors hereof, discloses such a form-block molded from foamed plastic. The voids which receive the concrete are formed during the molding of the block and the block material provides excellent insulation in the finished structure. Inner and outer wall surfaces such as gypsum board and stone may be placed as inserts in the mold used to form the block or these materials may be attached to the block after molding. These blocks provide important advantages over more conventional methods of reinforced concrete construction, both in economies achieved during the erection and the energy conserving properties of the resulting structure, which are attributable to the excellent insulating properties of the foam plastics employed in the blocks; however, recent price increases in petroleum-based foam plastics, and more particularly in the fire resistant varieties which must be employed in highrise structures has severely limited the use of these blocks.